More than 56 million people flew on U.S. commercial flights in November and only 1,300 filed complaints with the federal government. That's a rate of one complaint for every 43,000 passengers.

That rate may be hard to believe, given the shrinking of airline seats and the expansion of passenger fees over the last few years.

Rep. Janice Hahn (D-Los Angeles) believes that the number of complaints are relatively low because airlines have made it too hard to file a complaint with the U.S. Department of Transportation.

Under 2012 federal law, all airlines must post on their website information to help unhappy passengers file a complaint with the federal agency. A complaint can be made through a hotline (202-366-2220) or using an online complaint form.

But finding such information on an airline website isn't so easy. When Hahn's staff sought the information on the website for Spirit Airlines, they found it buried on page 48 of a 51-page legal document called the “Contract of Carriage.”

On American Airlines' website, the complaint information is at the bottom of a page titled “Consumer Service Plan.” At Delta Air Lines' website, the complaint information is near the bottom of a page titled “Travelers With Disabilities.”

“I searched for the hotline number myself on different airline websites and couldn't find it anywhere,” Hahn said. “If I can't find it, I am assuming many other fliers can't find it either, and the data demonstrates that.”

To address the problem, the lawmaker filed an amendment last week to a funding bill for the Federal Aviation Administration, requiring that the airlines post the complaint information on a prominent place on their websites.

In response to the amendment, American Airlines said: “We comply with all current regulations and will continue to do so.”

To read more about travel, tourism and the airline industry, follow me on Twitter at @hugomartin.